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The Vibrodens® slip form process produces concrete weight coatings with more consistent and uniform coating thickness, consistent reinforcement placement, a perfect moisture barrier, no damage to corrosion coatings, and compressive strength that meets the most rigid requirements.
The Vibrodens® concrete coating method results in a high quality concrete, whereby a weight coating is produced with the following unique characteristics:
• Concrete density up to 3700 kg/m3
• Low absorption coefficient of approximately 0.4%
• Exact uniform outer dimensions
• Perfect embedding of reinforcement cages
The high density concrete achieved with the slip form technique provides considerable savings in the consumption of cement and iron ore as well as manpower.
The Vibrodens® Method
Quality concrete requires strictly controlled procedures for mixing and application. The Vibrodens® method has been developed to take advantage of the important effect of vibration to produce a dense concrete coating using the optimal composition of cement and aggregates, including iron ore.
The concrete mix is applied to the vertical pipe by a purpose designed slipform process, which allows the coated pipe to be handled immediately after the slipform has been raised along the pipe.
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Cut-away drawing showing batching plant, concrete conveyor and coating tower with tilting mandrill, elevator platform and top mandrill.
The coating Tower
The coating tower is equipped with a tilting mandrill, elevator platform and a top mandrill.
The tilting mandrill turns the anti-corrosion coated pipe, including the reinforcement cage, to the vertical position.
The concrete is produced on site by a fully automated batching plant and by conveyor it is brought onto the elevator platform where the rotor distributes the concrete evenly around the pipe and into the cylindrical mould.
Through the effect of electromagnetic vibrators, perfect compaction is achieved during the raising of the platform with the concreting equipment.
Immediately after completion, the coated pipe is tilted back to a horizontal position, and simultaneously the next pipe is brought to vertical position.
Handling of the freshly coated pipe in this manner is possible because a minimum of water is added to the mix, resulting in a no-slump concrete.
The Vibrodens® method produces a dense and smooth concrete surface complying exactly with the outside diameter specified.
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| Density of Concrete |
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Concrete can be produced with a density anywhere in the range from 2400 kg/m3 to 3700 kg/m3.
Adjustment of the density is achieved by varying the amount of iron ore in the mix.
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| Compressive strength |
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| Apart from well graded aggregates, the compressive strength depends mainly on cement and water content. To maintain the necessary cohesiveness of the fresh concrete, the cement content cannot be less than 300 kg/m3 which will produce a compressive strength of 40-45 MPa. The relationship between cement content and compressive strength is illustrated by the graph. |
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